Lecture 16: Composition of fruits and veg

Question 1

max moisture content at complete turgor yield ____ turgidity

Answer 1

max

Question 2

how can a plant have complete turgor?

Answer 2

having unlimited supply from mother plant

Question 3

describe the conditions (TSS, OP and TP) at a very tender stage of a crop

Answer 3

low total soluble solids (TSS)

low OP

low TP

Question 4

describe the conditions for optimal maturity stage of produce

Answer 4

high OP and TP = high turgidity

- balanced starch, celulose and pectin

Question 5

describe the conditions of overmaturity/ripening

Answer 5

fruits:
- breakdown of starch and pectin
- loss in cell wall strength
- decr in turgidity

veg

• sugar becomes starch
• loss of TSS
• low OP
• low turgidity despite high cell wall strength

Question 6

what is imp about dietary fiber consumption?

Answer 6

1. provides non-digestable bulk to the diet
2. helps to control appetite = incr retention time for nutrients
3. restricts calorie food intake
4. delays absorption of glucose and fat after a meal

Question 7

what are 2 main categories of dietary fibers? example of each?

Answer 7

insoluble: cellulose, hemicellulose, lignin
soluble: pectin and gums

Question 8

describe resistant starches

Answer 8

• new class of fiber
• not easily digestible
• retains longer in the system
• good for diabetic patients

Question 9

describe straight chain starches

Answer 9

amylose w/ alpha 1,4 bonds

Question 10

describe branched chain starches

Answer 10

amylopectin (alpha 1-4 and 1-6 bonds)

Question 11

what bonds does cellulose have

Answer 11

beta 1-4 linkages

Question 12

what major enzymes breaks down starches?

Answer 12

amylase and beta-galactosidase

Question 13

industrially, starch is obtained from what?

Answer 13

potato and corn

Question 14

describe pectic substances

Answer 14

• imp for texture of produce due to structure forming ability
• polymer of methyl ester of galacturonic acid
• forms gel or viscous colloidal suspensions (eg. jam = pectin + sugar + acid + cooking)

Question 15

what are rich sources of pectin?

Answer 15

apple and citrus fruits

Question 16

what are 4 types of resistant starches?

Answer 16

RS1:

• physically inaccessible or digestible
• found in seeds and unprocessed whole grains

RS2
- occurs in natural granular form (uncooked potato, high amylose corn, green banana)

RS3
- formed when starch containing foods are cooked and cooled (eg. bread or retrograded high amylose corn)

RS4

• starches that have been chemically modified to resist digestion
• not found in nature

Question 17

what are main components of jam?

Answer 17

pectin
sugar
acid

Question 18

what is LMP? describe it.

Answer 18

low methoxyl pectin

• forms gel with Ca without sugars
• used in making diabetic jellies

Question 19

how does pectic substances affect fruit juices?

Answer 19

• increases viscosity
• incr cloudiness
• colloidal suspension

Question 20

what is PME? describe it.

Answer 20

pectin methyl esterase

- a natural enzyme that can hydrolyze pectin

Question 21

how can you decrease cloudiness of apple juice?

Answer 21

increase PME to hydrolyze pectin

then inactivate it during pasteurization

Question 22

what is calcium chloride treatment used for? how does this occur?

Answer 22

firming fruit slices

Ca forms a gel with pectin (LMP) to increase gel strength or structural rigidity

Question 23

how does pectin affect filtration in juice making?

how can this be prevented?

Answer 23

• it delays filtration

- can facilitate filtration by using PME to breakdown pectin and using amylase to breakdown starch

Question 24

____ are the major components of the cytoplasm

Answer 24

protein

Question 25

define dry weight basis

Answer 25

%DB = (wt x 100) / dry mass

Question 26

define wet wt basis

Answer 26

%DB = (wt x 100) / wet mass

Question 27

during storage, how do proteins affect OP of AA? how does this affect nutrition of the crops?

Answer 27

lowers OP of AA increases nutrition of crops

Question 28

what are common plant proteins?

Answer 28

albumins globulins gliadins glutenin

Question 29

what does gluten consist of?

Answer 29

gliadins and glutenins

Question 30

what is gluten imp for?

Answer 30

dough rheology

Question 31

what are fats and oils prominent in?

Answer 31

protective tissues (cuticle, epidermis, corky layers)

Question 32

what does the nutritional value of a fat/oil depend on?

Answer 32

degree of unsaturation

Question 33

what are examples of oils rich in sat FAs?

Answer 33

coconut and palm kernel oils

Question 34

what are examples of oils rich in unsat FAs?

Answer 34

corn peanut olive soybean

Question 35

how many double bonds are in oleic acid? in linoleic? in linolenic? in stearic?

Answer 35

oleic: 1 DB linoleic: 2 DB linolenic: 3 DB stearic: no DB (saturated)

Question 36

how are organic acids formed in F&V?

Answer 36

by products of metabolic activities

Question 37

where are organic acids normally stored?

Answer 37

in the vacuole

Question 38

what are dominant organic acids?

Answer 38

citric and malic others: tartaric, oxalic, isocitric

Question 39

what is used as a common food acidulant? why?

Answer 39

lime and lemons they have more than 3% organic acid

Question 40

what is EPA? describe it

Answer 40

- eicosa pentenoic acid - omega 3 FA - found in large amounts in brain nerve - v imp in immune system function - found in oily fish, seeds and nuts

Question 41

how is vit A present in F&V? how is it converted to vit A?

Answer 41

as pro-vitamin A (beta-carotene) which is converted to vit A in digestive system

Question 42

why is Ca in spinach not bioavailable?

Answer 42

it is bound to oxalic acid

Question 43

what are 3 major classes of pigments in F&V?

Answer 43

chlorophylls carotenoids falvonoids

Question 44

describe chlorophylls

Answer 44

- normal green pigments - imp for photosynthetic activity - found in chloroplast (chlorophyll a and b) - broken down by enzyme chlorophyllase

Question 45

what color are carotenoids?

Answer 45

yellow, orange they are masked by chlorophylls in green leaves

Question 46

describe solubility of carotenoids

Answer 46

fat soluble

Question 47

where is beta-carotene found? lycopene? xanthophylls?

Answer 47

beta-carotene: carrot lycopene: tomato xanthophylls: radish

Question 48

where are carotenoids most present in plants?

Answer 48

chromoplasts

Question 49

how does chlorophyll (green) become phyophitin (olive green)

Answer 49

loses Mg | gains H+

Question 50

how does phyophitin (olive green) become phyophobide (brown)

Answer 50

loses phytol

Question 51

how does chlorophyllin (bright green) become phyophobide (brown)

Answer 51

loses Mg

Question 52

how does chlorophyll (green) become chlorophyllin (bright green)

Answer 52

loses phytol

Question 53

how does chlorophyllin (bright green) become chlorins (purpurins colorless)

Answer 53

H+ or O2

Question 54

how does phyophitin (olive green become chlorins (colorless)

Answer 54

O2

Question 55

which pigment is responsible for bright colors in F&V?

Answer 55

flavonoids

Question 56

what are classes of flavonoids?

Answer 56

anthocyanins: - red, blue, purple - found in sap of fruits, stems leaves roots anthoxanthins: - yellow - shade is pH dependent catechins leucoanthocyanins:: colorless but forms brown pigments

Question 57

what does the shade of anthocyanin depend on? what colors are they in low, medium and alkaline pH?

Answer 57

pH low pH: red with increasing pH: violet alkaline pH: blue

Question 58

where are anthocyanins found?

Answer 58

sap of fruits, stems, leaves, roots

Question 59

what happens when tannins reacts with skin?

Answer 59

- produce tan color | - produced by polymers of catechin in reaction with proteins of skin

Question 60

what happens when tannins reacts w/ metal ions? what is this commonly used for?

Answer 60

dark colors used in making inks

Question 61

what is the dark color of coffee and tea from?

Answer 61

tannins

Question 62

what are anti-nutritional factors? examples?

Answer 62

- foods that can cause allergies, loss in memory, convulsions, paralysis, etc... - eg. excessive consumption of cabbage can cause hyperthyroidism (decreases iodine absorption)

Question 63

how can you cope with anti-nutrients?

Answer 63

inactivate toxins by cooking

Question 64

what happens when soybeans are soaked before cooking?

Answer 64

it removes thermo-labile toxic peptides (protease inhibitors)